AME8803_08 Datasheet, PDF(10/19 Page) Analog Microelectronics

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AME8803_08 Datasheet, PDF (10/19 Pages) Analog Microelectronics – 300mA CMOS LDO

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AME

AME8803 / 8814

n Detailed Description

The AME8803/8814 family of CMOS regulators con-

tain a PMOS pass transistor, voltage reference, error am-

plifier, over-current protection, thermal shutdown, and

Power Good detection circuitry.

The P-channel pass transistor receives data from the

error amplifier, over-current shutdown, and thermal pro-

tection circuits. During normal operation, the error ampli-

fier compares the output voltage to a precision reference.

Over-current and Thermal shutdown circuits become ac-

tive when the junction temperature exceeds 150oC, or

the current exceeds 300mA. During thermal shutdown,

the output voltage remains low. Normal operation is re-

stored when the junction temperature drops below 120oC.

The AME8803/8814 switches from voltage mode to cur-

rent mode when the load exceeds the rated output cur-

rent. This prevents over-stress. The AME8803 also in-

corporates current foldback to reduce power dissipation

when the output is short circuited. This feature becomes

active when the output drops below 0.8volts, and reduces

the current flow by 65%. Full current is restored when

the voltage exceeds 0.8 volts.

n External Capacitors

The AME8803/8814 is stable with an output capacitor

to ground of 2.2ÂµF or greater. Ceramic capacitors have

the lowest ESR, and will offer the best AC performance.

Conversely, Aluminum Electrolytic capacitors exhibit the

highest ESR, resulting in the poorest AC response. Un-

fortunately, large value ceramic capacitors are compara-

tively expensive. One option is to parallel a 0.1ÂµF ce-

ramic capacitor with a 10ÂµF Aluminum Electrolytic. The

benefit is low ESR, high capacitance, and low overall cost.

A second capacitor is recommended between the in-

put and ground to stabilize Vin. The input capacitor should

be at least 0.1ÂµF to have a beneficial effect.

A third capacitor can be connected between the BY-

PASS pin and GND. This capacitor can be a low cost

Polyester Film variety between the value of 0.001 ~

0.01ÂµF. A larger capacitor improves the AC ripple rejec-

tion, but also makes the output come up slowly. This

"Soft" turn-on is desirable in some applications to limit

turn-on surges.

300mA CMOS LDO

All capacitors should be placed in close proximity to

the pins. A "Quiet" ground termination is desirable. This

can be achieved with a "Star" connection.

n Enable

The Enable pin normally floats high. When actively,

pulled low, the PMOS pass transistor shuts off, and all

internal circuits are powered down. In this state, the

quiescent current is less than 1ÂµA. This pin behaves

much like an electronic switch.

n Power Good

The AME8803/8814 includes the Power Good feature.

When the output is not within +15% of the specified volt-

age, it pulls low. This can occur under the following con-

ditions:

1) Input Voltage too low.

2) During Over-Temperature.

3) During Over-Current.

4) If output is pulled up.

(Note: PG pin is an open-drain output.)

Rev.I.02

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